Reinforced concrete parts for electrolytic cells



Sept. 10, 1968 A. R. ANDERSON REINFORCED CONCRETE PARTS FOR ELECTROLYTIC CELLS 2 Sheets-Sheet 1 Filed Sept. 28, 1964 Sept. 10, 1968 'A. R. ANDERSON 3,401,109

REINFORCED CONCRETE PARTS FOR ELECTROLYTIC CELLS Filed Sept. 28, 1964 2 Sheetsfiheet 2 United States Patent 3,401,109 REINFORCED CONCRETE PARTS FOR ELECTROLYTIC CELLS Arthur R. Anderson, Tacoma, Wash., assignor to Hooker Chemical Corporation, Niagara Falls, N.Y., a corporation of New York Filed Sept. 28, 1964, Ser. No. 399,594 9 Claims. (Cl. 204-242) ABSTRACT OF THE DISCLOSURE Reinforced shaped concrete parts for electrolytic cells are provided by pre-tensioning or post-tensioning reinforcing members. Optionally, the reinforming members may be inserted through tubular members encased in the concrete. The tubular members are preferably inert to the electrolyte housed within the cell.

This invention relates to reinforced concrete cell parts for electrolytic cells. More particularly, this invention relates to improvements of concrete cell parts for the electrolysis of solutions and to the concrete cell.

Reinforced concrete cell parts for electrolytic cells have been known and used for many years. Electrolytic cells constructed of concrete have numerous advantages over cells constructed of other materials. Concrete is relatively non-conductive of electrical current, highly resistant to corrosive liquids, relatively easy to fabricate, and is also low in cost. These and other reasons contribute to the fact that electrolytic cells for the electrolysis of brine, the manufacure of chlorates and perchlorates, and the like electrolytic processes are most frequently constructed of concrete.

Although concrete is a preferred material for electrolytic cell parts, it has a disadvantage which markedly reduces its useful life. It is known, that in the manufacture of concrete cell parts, reinforcing is required to support the considerable weight and stresses placed on the cells during operation. The use of reinforcing members, such as steel rods and cables, greatly increases the strength of the concrete and enables it to bear the required weight.

It is an object of this invention to provide concrete parts for electrolytic cells having greatly increased useful lives. Another object of this invention is to provide methods of applying a compressive force to the concrete cell part during or subsequent to the curing process. These and other objects will become apparent to those skilled in the art from the description of the invention.

In accordance with the invention there is provided a shaped concrete electrolytic cell structure under a compressive force applied thereto by means of structure reinforcing members therein.

In addition, in one of its aspects, the invention provides for protecting the reinforcing members so as to prevent corrosion and decomposition thereof if electrolyte solutions penetrate the concrete structure.

The structures of the present invention are produced by applying a tensile force to the reinforcing members often called tendons during the production of the cell component and transferring the applied tensile force to the concrete part, whereby a compression force is exerted on the concrete. The application of the tensile force can be made either prior to, during, or subsequent to the cure of the concrete surrounding the tendons. Depending on whether the tensile force is applied prior to cure or subsequent thereto, a different method of producing the reinforced structure is used. Irrespective of the method used, the end result is the application of a compressive force t the concrete through the reinforcing member.

Patented Sept. 10, 1968 The methods of producing the structure of this invention can be broadly classified as a pre-tensioning meth- 0d and a post-tensioning method. The term pre-tensioning designates applying a tensile force to a reinforcing member prior to the cure or set to a rigid state of the concrete surrounding the reinforcing member. Pre-tensioning a reinforced concrete cell part may be effected by distributing reinforcing members in a spaced relationship within a mold, applying a tensile force to at least one reinforcing member in an amount of 20 percent to percent of the members ultimate tensile strength, casting concrete about the tendon, at least partially curing said concrete and transferring the tension in the tendon to the concrete by anchorage through bond.

The term post-tensioning designates the process of applying a tensile force to a reinforcing member subsequent to at least a partial cure. In the post-tensioning technique, an improved reinforced concrete cell part is made by distributing one or more open ended tubular members in a spaced relationship to other tubular members within a mold, casting concrete about the tubular member, at least partially curing said concrete prior to removing from the mold, inserting a reinforcing member through the tubular member, applying a tensile force to the inserted reinforcing member, and transmitting this force as a compressive force to the molded structure by permanent and anchoring devices.

The effect of both the pre-stressing and post tensioning methods is the application of a compressive force on the concrete structure ranging from an average of 50 pounds per square inch (p.s.i.) to 3000 p.s.i. Preferably, the compressive force averages 300 to 1200 p.s.i. throughout the concrete structure. To obtain the preferred compressive force, the cross-sectional area of the structure is taken into account in addition to the number of reinforcing members used. Reinforcing members are used in sulficient quantity and of sufficient tensile strength so as to be capable of supporting the required compressive force. Thus, for example, to obtain a compressive force of 500 p.s.i. on a cross-sectional area of 864 square inches using six reinforcing members, each reinforcing member would have to apply a 72,000 pound force to the structure. Using reinforcing members such as steel cables and applying a force not exceeding 70 percent of the cables ultimate strength would require a 103,000 p.s.i. cable. It is thus seen that the tensile force applied to the reinforcing members can vary between wide limits depending on the number of reinforcing members, the cross-sectional area and the final compressive force desired. In essence, the tensile force applied to the reinforcing members can range from about 50 p.s.i. to about 3,000,000 p.s.i., but as a practical matter would normally range from about 1000 p.s.i. to 500,000 p.s.i.

In the post-tensioning technique, a base plate is used to which the cable is anchored. The base plate is of suflicient size and area so as to disperse the compressive force along the face of the concrete structure and thereby distribute the compressive force to a large surface area. Thus, the compressive strength of the concrete is not as likely to be exceeded in the portions of concrete nearest to the stressing means, as when no base plates are used. It is seen that the number of reinforcing members and their required strength is readily determined for any size structure based on the desired amount of compressive force to be applied.

The concrete used with this invention is comprised of an aggregatematerial, cement and water. The aggregate material is similar to that normally used in concrete mixes and preferably ranges in size from about one inch in diameter to a fine sand. It is preferred that the amount of fines, less than about 50 to 60 mesh contained in the aggregate mixture, be held to a minimum. As the amount of fines increases, the cement requirement increases, too. The aggregate type is preferably of granite, slag, stone 'or the like hard, insoluble stone.

The cement used may be type I, II, III, IV or V as defined by American Society "for Testing Materials specifications C150 and C175. The concrete mix can be used either with or without air entrainment. Type III cement is a fast setting cement and under normal operating conditions it is preferred in that a faster strip time is achieved. Type III witha low slump (minimum water content) is a preferred mix. The ratio of cement aggregate and water is the normal ratio used for low slump concrete.

The invention will be described with reference to the drawing in which:

FIG. 1 is a side elevation of a typical electrolytic cell, shown disassembled, in which the subject of this invention has been included;

FIG. 2 is a top plan view of a mold for a cell component and a jacking device for tensioning reinforcing members;

FIG. 3 is a partial vertical sectional view of the concrete cell structure and reinforcing member along 33 of FIG. 1; and

FIG. 4 is a partial sectional view of the concrete cell structure and reinforcing member along 4-4 of FIG. 1.

An electrolytic cell for the electrolysis of brine, chlorate, perchlorate, hydrochloric acid and the like, is composed of several concrete parts. FIG. 1 shows a typical electrolytic cell in its several parts, having a concrete cell top 11, a metallic cathode 12, conductive anodes 18, a concrete cell bottom 14, and supports 16. The concrete cell top 11 and concrete cell bottom 14 are reinforced by reinforcing members and 21. The cell 10, when assembled for operation, has the cathode 12 resting on the cell bottom 14 and the cell top 11 resting on the cathode 12.

The reinforcing members 20 and 21 are normally of metal such as iron, steel and the like high tensile strength materials. The reinforcing members can be in the form of solid bars, cables, wires and the like, having relatively low stretching characteristics and high tensile strength.

Cold drawn, stress relieved strand cable is particularly useful. In the practice of this invention it is not necessary for the reinforcing members 20 and 21 to be of high transverse strength. Therefore, as is generally true of cables and wires, the reinforcing member can be relatively flexible.

In pre-tensioning, one may employ a jacking frame 22 which is placed about a mold 24 of the desired shape. Reinforcing members 20 are passed through mold 24 and anchored to jacking frame 22. The reinforcing members 20 are then placed under a tensile force ranging from 20 percent up to 80 percent of their ultimate strength. Preferably, a tensile force of about 70 percent of the ultimate strength of the reinforcing member 20 is applied. After application of the desired tensile force, the reinforcing member 20 is held by the jacking frame 22 at the applied force by means of locks 26. Mold 24 is positioned by mold holding device 28 so that the reinforcing members 20 are in a spaced relationship to each other through the mold and are located so as to be encased by concrete during the casting process.

After the casting of concrete about the reinforcing members 20 so as to completely fill the mold 24 to the desired level, the concrete is allowed to cure. During the curing process, the reinforcing members 20 are bonded to the concrete 30. The applied tensile force in each supporting member is then released in one or more steps, thereby effecting a transfer of the applied tensile force to the concrete as a compressive force due to adherence of the reinforcing member to the concrete or its being locked in place. Finally, the protruding reinforcing members are removed flush with the shaped structure and coated with a sealing compound 32, to protect the exposed ends from corrosive attack. The concrete cell top 11 of FIG. 1 illustrates the above-described embodiment. The sealing compound 32 is a material which is inert to caustic, brine, hydrochloric acid and the like electrolyte, and other corrosive chemicals likely to come into contact therewith, and which is resistant to. temperatures up to 100 degrees centigrade. Sealing compounds such as grout, plaster, putty, and polymeric organic resins such as epoxy resins, phenolic resins and polyesters are preferred.

The application of the post-tensioning method in the production of electrolytic cells in accordance with this invention is effected by placing hollow tubular member 36 in the mold and positioning it so as to traverse the mold from one side to another. The tubular reinforcing members are placed in a spaced relationship to each other so as to be ultimately separated by concrete. Concrete is then cast into the mold so as to surround and envelop the reinforcing members. After having effected at least a partial cure of the cast concrete, such cure being sufficient so as to enable removal from the mold, a reinforcing member 21 is inserted and passed through tubular member 36. The inserted reinforcing member 21 is then anchored at one end of the cast structure and a tensile force equal to about 20 percent to not more than about percent of the ultimate tensile strength of the inserted reinforcing member 21 is applied. The space 38 between inserted reinforcing member 21 and tubular member 36 is preferably filled with grout, concrete, organic resin or the like so as to securely bind the inserted member 21 to the tubular member 36 and thereby effect a transfer of reinforcing strength to the tubular reinforcing member 36 and the concrete 30. Alternately, the tubular member 36 can be removed prior to inserting the reinforcing member 21 and the space 38 filled with concrete, resin, etc., to effect a direct transfer of reinforcing strength.

Having placed the reinforcing member 21 under a tensile force, plate 34 and lock 26 are inserted around the reinforcing member 21 so as to retain permanently the reinforcing member 21 under a tensile force. The tensile force retained in reinforcing member 21 affects a compressive force on the concrete cell structure, transferred to the structure by means of end plate 34.

The tubular member 36 used in the post-tensioning method is constructed of metal, cardboard, or more preferably a plastic which is inert and impervious to electrolyte. Such synthetic organic plastic materials as polyvinyl chloride, rechlorinated polyvinyl chloride, polytetrafluoroethylene, polypropylene, polyester, reinforced polyester, epoxy resin, reinforced epoxy resin, phenolic resin, and the like non-corrodible materials are preferably used. The strength requirement of the tubular material is only that sufficient to retain its tubular shape during the casting process. In the completed cell structure, inert plastic tubular member 36 provides a means of encasing the reinforcing member with an impervious boundary and thus prevents contact with electrolyte if the electrolyte should penetrate to the tubular member.

The protruding ends of the reinforcing member and the locking device therefor can also be coated with an inert resin as previously described so as to further protect them from corrosion.

The invention will be readily understood from reference to the following examples which are illustrative of certain preferred embodiments of the present invention. Unless otherwise indicated all temperatures are in degrees centrigrade and all parts and percentages used herein are by weight.

EXAMPLE 1 A pre-stressed concrete cell bottom was prepared by casting a zero slump concrete mix made from Type III cement into a suitable mold having seven strand 250,000 p.s.i. steel cable passing through the mold. A jacking frame, as illustrated in FIG. 2, was placed about the mold. The mold was of a size and shape to produce a commercial production cell bottom 6 feet by 6 feet by 1 foot. The jacking frame was of a size such that when the mold was centered within the jacking frame, a one foot clearance separated the mold from the jacking frame. The steel cables were spaced at distances about one foot apart, parallel and at right angles toeach other so as to produce the appearance of dividing the mold into areas about one foot square, The cables were then placed under tension by means of a hydraulic ram to within about 80 percent of their ultimate tensile strength or approximately 180,000 to 200,000 pounds per squareinch.

The prepared zero slump concrete was then cast into the mold and cured at a temperature of 35 degrees centigrade to 48 degrees Centigrade until an initial set or cure was effected. The initialcure was effected in 16 to 24 hours, after which the green casting was removed from the mold. Following the initial cure, the green casting was subjected to a periodof moist curing for 7 days and air curing for 21 days. The 28 day cure resulted in a concrete having a minimum compression strength of 6000 pounds per square inch and averaging 10,000 pounds per square inch.

Upon completion of the 28-day cure the tension applied to the cables was released and the cable ends, projecting outside of the concrete structure, were cut off with a grinding wheel. The exposed ends were then protected by coating with an epoxy resin composed of a bisphenol A-epichlorohydrin condensate cured with a polyamine. There was a slight loss of tension in the cables due to steel creep, concrete shrinkage and elastic deformation of the concrete so that the final stress was about 80 percent of the initial stress or about 150,000 p.s.i.

Upon completion of the cure, the concrete cell bottom was carefully inspected for defects and cracks. The absence of minute cracks near the reinforcing members was noted. The prestressed concrete structure was then subjected to actual use to determine its performance. Frequent examination of the structure over an extended period of time during actual use did not detect failure of the formation of cracks or other indications of potential trouble. Control concrete structures of similar size and shape of standard manufacture installed at the same time as the pre-stressed structure failed during the testing interval as expected.

Additional cell structures were made in which the stress was released at varied curing intervals. It was found that the stress could be released to the green concrete as soon as 5000 p.s.i. compressive strength is attained, which can be achieved 16 hours after casting.

EXAMPLE 2 Concrete cell tops were also manufactured as described in Example 1. The different shape resulted in a different placement of the reinforcing cables. The cables were placed so as to reinforce the sides of the cell top, thereby providing two parallel and intersecting peripheral tensioried cables along each of the four sides.

The tops were also tested as in Example 1 and were found to exhibit greatly extended useful life over cell tops of standard manufacture.

EXAMPLE 3 Concrete cell bottoms were made by the post-tensioning technique of this invention using a cell bottom mold similar to that of Example 1. inch hollow polyvinyl chloride pipes were positioned in the mold so as to cross the width and length of the mold in a spaced relationship to each other, having the ends of the tubes flush with the inside of the mold. The placement of the tubes was such that the passages through the tubes would not be blocked with concrete. Six tubes were placed across the width of the 6 foot by 6 foot mold and five tubes were placed across the length of the mold. A zero slump concrete mix using Type III cement was cast into the mold so as to cover the tubes. An initial cure of the concrete was effected at a temperature of 40 degrees centigrade for 21 hours. The green concrete was then removed from the mold and reinforcing cables of 250,000 p.s.i. strength were passed through the tube passages. After the concrete reached a hardness of about 5000 psi. compressive strength, the spaces between the reinforcing cables and the tubes were filled with concrete. A tensile force of 175,000 to 190,000 pounds per square inch was applied to each cable. The tensioned cables were anchored to a base plate and secured on all sides of the concrete structure, thereby applying a compressive force to the structure. The excess cable was trimmed and the exposed ends and locking device were protected with a coating of epoxy resin.

1 Upon completion of the post-tensioning process, the cast structure was inspected for defects and hairline cracks. No significant cracks were noted.

Cell bottoms prepared by this method were then assembled for use as an electrolytic cell and were placed in operation to further observe their performance in actual use. The cells were inspected at frequent intervals over an eighteen month period during which time the cells did not fail, whereas cell bottoms of conventional manufacture installed at the same time failed during this period as was expected.

EXAMPLE 4 Concrete cell tops were prepared by the post-tensioning technique in the same manner as Example 3 with the exception that the /4 inch polyvinyl chloride tubing was placed so as to have two parallel tubes spaced about ten inches apart crossing each of the four sides of a 6 foot by 6 foot mold.

The concrete cell tops prepared in this manner were also tested and compared to cell tops of standard manufacture and found to have a longer useful life.

While there have been described various embodiments of the present invention, the apparatus and methods described are not intended to be understood as limiting the scope of the invention as it is realized that changes therein are possible and it is further intended that each element recited in any of the following claims is to be understood as referring to all equivalent elements for accomplishing substantially the same result in substantially the same or equivalent manner. It is intended to cover the invention broadly in whatever form its principles may be utilized.

What is claimed is:

1. An electrolytic cell having a cell top part and a cell bottom part comprised of shaped concrete structures, said parts having disposed therein reinforcing cables distributed in a spaced relationship to each other traversing the length and width of the cell part, said reinforcing cables being encased in concrete and being under an applied tensile force.

2. An electrolytic cell having a cell top part and a cell bottom part comprised of shaped concrete structures, said parts having disposed therein plastic tubular members, through which reinforcing cables pass, distributed in a spaced relationship to each other traversing the length and width of the cell part, said plastic tubular members being encased in concrete and said reinforcing cables being under an applied tensile force.

3. In an electrolytic cell having shaped concrete top and bottom parts, with metal reinforcing members embedded in the concrete of at least one of said parts, the improvement which comprises having at least one of said concrete parts under a compressive force applied by means of said reinforcing members.

4. The electrolytic cell of claim 3 in which said reinforcing members are under an applied tensile force between about 20 percent to about percent of the mem bers, ultimate strength, said members applying a compresive force on the concrete in which they are embedded in an amount between about 50 to 3000 pounds per square inch.

5. The electrolytic cell of claim 3 wherein the reinforcing members under an applied tensile force are embedded in the shaped concrete cell top and the shaped concrete cell bottom, said reinforcing members being distributed in a spaced relationship to each other traversing the length and width of said cell top and cell bottom.

6. The electrolytic cell of claim 3 in which said reinforcing members are steel cables.

7. The electrolytic cell of claim 6 in which the terminal ends of said reinforcing cables are covered with a sealing means.

8. In an electrolytic cell having a shaped concrete top and bottom, the improvement which comprises disposed plastic tubular members encased in the concrete, said tubular members having inserted therethrough reinforcing members, said reinforcing members being under a tensile force, the terminal ends of said reinforcing members having anchoring means to a. base plate on the concrete cell 20 part, said reinforcing members thereby exerting a compressive force on the concrete cell part.

9. The electrolytic cell of claim 8 wherein the space between the inserted reinforcing members and tubular mem- I References Cited UNITED STATES PATENTS 2,890,157 6/1959 Raetzsch 204 2ss XR 1,866,065 6/1932 Stuart 204-258 2,234,663 3/ 1941 Anderegg 264-228 2,590,685 3/1952 Colf 52-230 X 2,618,147 11/1952 Freyssinet 52-230 3,036,356 5/ 1962 Greulich 264-228 3,060,640 10/1962 Harris 52-230 3,086,273 4/1963 Welborn 52-223 X 3,293,139 12/1966 Bellier 52-224 X FOREIGN PATENTS 571,901 9/1945 Great Britain.

JOHN H. MACK, Primary Examiner.

HOWARD S. WILLIAMS, Examiner.

D. R. JORDAN, Assistant Examiner. 

